1. Field of the Invention
The present invention relates to novel bacteria which inhibit the formation of dental plaque in human mouths. More particularly, the present invention relates to novel lactic acid bacteria capable of inhibiting the formation of glucan, a major component of dental plaque, in human mouths, which is produced from the microorganisms which normally inhabit in human mouths. These lactic acid bacteria are of the genera Enterococcus, Lactobacillus, and Lactococcus, and Lactococcus spp. which are thought to inhibit the activity of glucosyltransferase or to antagonize against the bacteria which play a role in forming glucan.
2. Description of the Prior Art
Lactic acid bacteria are those which ferment carbohydrates to produce lactic acid as a final product. Lactic acid bacteria live in the oral cavities and the alimentary tracts of men and animals and are utilized for the manufacture of fermentative foods, such as kimchi, yogurt, etc. In addition, they are reported to be used to produce biologically active materials, such as medicines. Among the lactic bacteria are those of the genera Streptococcus, Enterococcus, Lactococcus, Lactobacillus, and Bifidobacterium. Representative examples of these lactic acid-producing bacteria include Streptococcus thermophilus, Enterococcus faecalis, Enterococcus durans, Lactococcus lactis, Lactobacillus lactis, Lactobacillus acidophilus, Lactobacillus bulgaricus, Lactobacillus thermophilus, Lactobacillus casei and Lactobacillus plantarum. As inhabitants in the entrails of men and animals, these lactic acid bacteria, Gram-positive bacteria, are known to play an important role in maintaining the entrails healthy condition by utilizing carbohydrates as energy source to produce lactic acid and antibacterial materials which inhibit the growth of the harmful bacteria.
In the past, enzymes which decomposed glucan, the major component of dental plaque, were isolated to be useful for the sanitization of oral cavity. For example, dextranase (.alpha.-1,6 glucan hydrolase) which used dextran as a substrate was purified and applied to animals and men (Staat, R. H. and Schachtete, C. F., 1975; Kaster, A. G. and Brown, L. R., 1983). In addition, it was reported that mutanase (endo-.alpha.-1,3-glucanase) which decomposed mutan, an important component for the formation of glucan, was isolated and purified and had an inhibitory effect on the formation of dental plaque (Guggenheim B., et al., 1972; Takehara et al., 1981). However, these inhibitory enzymes against glucan formation were found to have an insignificant effect in human oral cavities. For mutanase, the decomposition effect of dental plaque is trivial and it takes a long time to express its effect. In addition, since tremendous effort and time are required for the isolation and purification of the enzyme, it is problematic in the economical and practical aspects.